textproduct: Albany

WHAT HAS CHANGED

Models have shown a consistent trend in a cooler boundary layer for the system impacting the region through the remainder of the afternoon into tonight. Therefore, the primary wintry precipitation types have changed to sleet and snow as opposed to largely freezing rain. That said, the potential for freezing rain still exists, especially late this evening into the overnight in portions of the Southern Adirondacks, Southern Greens, Berkshires, Litchfield Hills, and Catskills. However, with the warm nose now expected to quickly erode, the window of opportunity for freezing rain has become shorter in duration. This has led to the reduction of ice amounts particularly in portions of the Hudson and Mohawk Valleys. But, given the expectation for some ice accretions in addition to some sleet and/or snow, the Advisories have remained unchanged.

KEY MESSAGES

1) A slippery morning commute can be expected across much of eastern New York and western New England due to overnight mixed precipitation.

2) Confidence remains high in above-normal temperatures late this weekend into the middle of next week which, combined with multiple chances for rain, could pose the threat of river rises; ice break up; and subsequent ice jams.

DISCUSSION

KEY MESSAGE 1... An initial batch of stratiform rain that had been impacting areas south of the Capital District throughout the morning has been reduced to mere scattered showers ahead of the next batch of stratiform precipitation that remains upstream. While isolated pockets of freezing rain were noted this morning in the Mid-Hudson Valley, temperatures have all risen well above freezing as of this afternoon, so any precipitation now reaching the ground is in the form of plain rain...and a cold one at that considering most haven't made it out of the mid-upper 30s.

Presently, a mid-level shortwave lies over the Ohio Valley with a surface trough just beneath. In response to this shortwave deepening slightly this evening, a surface low will take shape and track eastward, extending a horizontal warm front through the Mid-Atlantic. Isentropic lift and warm air advection will subsequently increase across the region from south to north, providing sufficient low-level support for ascent that will be maintained aloft by the CVA associated with the mid-level shortwave. This will allow the aforementioned area of rain to spread into our region from southwest to northeast later this afternoon.

Now, the complicating factor with this forecast is the potent anticyclone currently positioned just to the northeast of the northern tip of Maine. More or less easterly flow across the region as a result of this high will eventually provide counter-acting cool air advection to the warm air advection provided by the incoming system. The interaction of the two airmasses will ultimately lead to the development of a low-level warm nose, especially across higher elevations where cold air will be dammed against eastward-facing slopes, this evening that will allow rain to transition initially into freezing rain. This cold air damming will be particularly efficient for portions of the Southern Green and Berkshire Mountains courtesy of their adjacency to the high and the cool, western Atlantic air that the easterly flow regime is promoting. That said, some isolated pockets of freezing rain could also develop within the Southern Adirondacks and potentially the Eastern Catskills. Confidence is not as high in the potential for freezing rain in the Catskills, however, due to marginal thermal profiles.

Over the last couple of days, freezing rain actually looked like it would be the primary wintry precipitation type overnight tonight for many areas, not just the higher elevations. However, the last several runs of the HiRes guidance have indicated consistency in sleet actually winning over the freezing rain. The reason for this owes directly to the position of the aforementioned anticyclone. Previously, its position relative to our region was looking to be more or less overhead which would have allowed shallow cold air to sink farther through our area and not have as great of an impact on the warm nose. However, it has now consistently remained off to our northeast, placing us in more of an easterly to northeasterly flow regime that will more sufficiently counteract the southerly flow about the incoming low. This should significantly limit the duration and magnitude of the warm nose, allowing the initial freezing rain to transition to sleet and even snow as the boundary layer continues to cool overnight. Given this trend, we reduced ice accretions primarily across the Hudson and Mohawk Valleys and kept freezing rain isolated to late this evening/early tonight and early tomorrow morning when precipitation rates drop and supercooled drops could reach the ground before completely freezing.

All that said, we still anticipate multiple precipitation types tonight including snow, sleet, rain, and localized freezing rain. Given the anticipation of slippery conditions for the morning commute tomorrow, widespread trace up to 0.3" of ice, and widespread trace up to 2" of snow, we maintained the Winter Weather Advisories without any changes. Please take caution on the morning commute tomorrow. Many roads will be slick and travel may become difficult particularly in higher elevations.

KEY MESSAGE 2... Confidence continues to remain high in temperatures reaching above normal levels beginning this weekend into next week. That said, a series of weather systems may challenge how warm we actually get this weekend. A frontal system will bring widespread rain to the region Saturday leading to surface high temperatures rising only into the upper 40s to 50s despite 850 hPa temperatures rising to 2.5 STDEVs above normal. And, with this system's cold front reinforcing cold air advection across the region Sunday, highs will only reach the upper 30s at higher elevations to potentially the upper 50s in portions of the lower Mid-Hudson Valley.

However, 850 hPa temperatures remain elevated through the beginning of the week, aligning with high pressure at the surface to allow high temperatures to reach the 50s and 60s by Monday, Tuesday, and Wednesday. Additional chances for rain return late Tuesday potentially into Wednesday which may challenge highs for Wednesday, but we will monitor this over the coming days.

Between the warmer temperatures and several chances for rain, we are going to continually monitor rivers very closely. At this point, most have pretty significant ice depths, but sufficient warming, snow melt and subsequent runoff, and additional rainfall could lead to rises, ice break up, and potentially ice jams that may cause flooding. It is difficult to say at this time where there may be issues, but know that it is something we are monitoring very closely and will provide updates on promptly when we have additional information.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

Through 12z Friday...Rain will continue to affect the KALB/KPOU/KPSF sites this afternoon. As the precip expands northward by this evening, colder air in the low levels will gradually filter southward. So KGFL is expected to see a mix of RA/IP, changing to PL/SN and eventually SN overnight. KALB/KPSF will see a transition from RA to FZRA/PL this evening into the overnight hours. At this time KPOU is expected to remain warm enough for RA. The precip is expected to end from NW to SE between 10z-11z. Flying conditions will deteriorate to MVFR then IFR into this evening. Solid IFR conditions expected overnight into early Friday morning even after the precip ends due to abundant low level moisture trapped beneath an inversion. However, vsby should improve by late Friday morning. Winds through the period will be north-northeast around 3-8 kt.

Outlook...

Friday Night: Moderate Operational Impact. Chance of RA. Saturday: Low Operational Impact. Slight Chance of RA. Saturday Night: High Operational Impact. Definite RA. Sunday: No Operational Impact. NO SIG WX. Sunday Night: No Operational Impact. NO SIG WX. Monday: No Operational Impact. NO SIG WX. Monday Night: No Operational Impact. NO SIG WX. Tuesday: No Operational Impact. NO SIG WX.

ALY WATCHES/WARNINGS/ADVISORIES

CT...Winter Weather Advisory from 5 PM this afternoon to noon EST Friday for CTZ001-013. NY...Winter Weather Advisory from 5 PM this afternoon to noon EST Friday for NYZ032-033-038>043-047>054-058-061-063-082>084. Winter Weather Advisory from 8 PM this evening to noon EST Friday for NYZ059-060-066. MA...Winter Weather Advisory from 5 PM this afternoon to noon EST Friday for MAZ001-025. VT...Winter Weather Advisory from 5 PM this afternoon to noon EST Friday for VTZ013>015.